Experimental Drug Derived From Snake Venom Shows Promise In Reversing Effects Of Stroke

February 04, 1999

NASHVILLE, Feb. 4 -- A stroke therapy derived from snake venom? According to researchers, it's not a snake oil story, but instead a possible new way to help people recover from the devastating effects of stroke.

Scientists announced the results of a 500-person trial examining the effects of an experimental stroke drug called ANCROD here today at the 24th American Heart Association International Conference on Stroke and Cerebral Circulation.

Researchers found that 42 percent of stroke victims treated with ANCROD within three hours of stroke onset had recovered the physical and mental abilities that they had prior to the stroke.

In comparison, 34 percent of those receiving an inert substance, or placebo, regained their previous faculties. However, stroke patients who received ANCROD were also at a higher risk of bleeding in the brain (5 percent of patients) when compared to those who received the placebo (2 percent).

ANCROD is not yet approved by the Food and Drug Administration for stroke treatment. Tissue plasminogen activator (TPA) is the only FDA-approved acute stroke treatment.

ANCROD is derived from the venom of a pit viper snake. Researchers discovered that in people who were bitten by the snake, blood failed to clot. Based on that observation, the venom was utilized as an anticoagulant, helping blood flow more freely through vessels.

"Like clot-dissolving drugs TPA and urokinase, the goal was for ANCROD to be administered within three hours of stroke onset," says the study's lead author, David Sherman, M.D. "Also, none of these three drugs are for use in patients who have hemorrhagic strokes, caused by a burst or leaking blood vessel in the brain."

There are sharp contrasts between the treatments, however, says Sherman.

TPA is administered in a single-dose, hour-long injection and results can be seen soon thereafter. ANCROD is given intravenously through a catheter over a 3-to-5 day span in the hospital. While TPA dissolves the clots causing the most common type of stroke, ANCROD lowers the level of fibrinogen in the bloodstream.

Fibrinogen is a clotting factor that is produced naturally by the body. It can help form clots that can in turn block blood flow to the brain, resulting in a stroke. ANCROD improves the bloods viscosity, a measurement of how well it flows through blood vessels.

"We found that patients who had their fibrinogen levels lowered promptly, within 6 hours, and maintained in the target range after treatment had the best response to the treatment," says Sherman, professor and chief, division of neurology, University of Texas Health Science Center, San Antonio.

The initial amount of ANCROD administered is determined by the patients blood fibrinogen level and body weight.

The additional amounts of ANCROD administered is adjusted based on the amount of fibrinogen in the blood, which is regularly monitored for 3-to-5 days during hospitalization, according to Sherman. By keeping the fibrinogen levels between 40-70 milligrams per deciliter of blood, Sherman says it's possible to reverse the effects of the initial stroke, minimize the bleeding risk and protect against a recurrent stroke during therapy.

"What I envision if ANCROD is approved is that the physician would have the option of using either TPA or ANCROD, based on what would be best for that particular patient," says Sherman. "Overall, TPA has been shown to be a little bit more effective than ANCROD, but it also carries a little bit more danger with the possibility of bleeding in the brain. It's also easier to use -- one shot, one hour and youre done."

"With ANCROD, you're treating someone for 3 to 5 days and making sure their fibrinogen levels dont get too low or too high. There's more of a user-friendliness with ANCROD in the sense that youre able to monitor the patient more closely as you move forward with the treatment."

In the study, patients were treated between 3-to-5 days and then followed up at 3 months post-stroke; their progress was measured by various tests to determine neurological damage and ability to function in a normal manner.

"We think that its probably going to turn out to be safer than TPA in terms of risk of bleeding," says Sherman. "With the new therapy, the effects of the drug are sustained for five days instead of an hour or two, without increasing the bleeding risk over time."

The major risk in using clot-busting drugs is bleeding, or hemorrhage, in the brain.

Sherman says that ANCROD should not be considered a clot-busting therapy like TPA or urokinase, even though it does have similar properties.

"It's given through an IV infusion, so in that sense its similar to TPA," says Sherman. "TPA is usually an hour-long infusion while ANCROD is continuous over three days so you dont have the dramatic changes in coagulation that you can get with other types of clot-dissolving therapy."
Media advisory: Dr. Sherman can be reached by phone at 210-617-5161. (Please do not publish numbers.)

American Heart Association

Related Stroke Articles from Brightsurf:

Stroke alarm clock may streamline and accelerate time-sensitive acute stroke care
An interactive, digital alarm clock may speed emergency stroke care, starting at hospital arrival and through each step of the time-sensitive treatment process.

Stroke patients with COVID-19 have increased inflammation, stroke severity and death
Stroke patients who also have COVID-19 showed increased systemic inflammation, a more serious stroke severity and a much higher rate of death, compared to stroke patients who did not have COVID-19, according a retrospective, observational, cross-sectional study of 60 ischemic stroke patients admitted to UAB Hospital between late March and early May 2020.

'Time is vision' after a stroke
University of Rochester researchers studied stroke patients who experienced vision loss and found that the patients retained some visual abilities immediately after the stroke but these abilities diminished gradually and eventually disappeared permanently after approximately six months.

More stroke awareness, better eating habits may help reduce stroke risk for young adult African-Americans
Young African-Americans are experiencing higher rates of stroke because of health conditions such as high blood pressure, diabetes and obesity, yet their perception of their stroke risk is low.

How to help patients recover after a stroke
The existing approach to brain stimulation for rehabilitation after a stroke does not take into account the diversity of lesions and the individual characteristics of patients' brains.

Kids with headache after stroke might be at risk for another stroke
A new study has found a high incidence of headaches in pediatric stroke survivors and identified a possible association between post-stroke headache and stroke recurrence.

High stroke impact in low- and middle-income countries examined at 11th World Stroke Congress
Less wealthy countries struggle to meet greater need with far fewer resources.

Marijuana use might lead to higher risk of stroke, World Stroke Congress to be told
A five-year study of hospital statistics from the United States shows that the incidence of stroke has risen steadily among marijuana users even though the overall rate of stroke remained constant over the same period.

We need to talk about sexuality after stroke
Stroke survivors and their partners are not adequately supported to deal with changes to their relationships, self-identity, gender roles and intimacy following stroke, according to new research from the University of Sydney.

Standardized stroke protocol can ensure ELVO stroke patients are treated within 60 minutes
A new study shows that developing a standardized stroke protocol of having neurointerventional teams meet suspected emergent large vessel occlusion (ELVO) stroke patients upon their arrival at the hospital achieves a median door-to-recanalization time of less than 60 minutes.

Read More: Stroke News and Stroke Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.